In U.S. Pat. No. 4,580,930 to Zinner, there is illustrated and described a toolholder having a rigid base jaw and a tapering clamping jaw defining a longitudinally extending insert receiving slot for releasably receiving a cutting insert which is clamped therein by a clamping force transversely directed to its major clamping surfaces. Irrespective of how tightly a cutting insert is clamped in an insert receiving slot, it can be undesirably and forcibly extracted therefrom during a cutting operation by outwardly directed unseating forces acting co-directional with the slot. To prevent such unseating, the toolholder is provided with a stopping member (28) received in a recess (27) formed in the cutting insert's lower clamping surface (see FIG. 12). However, this complicates the toolholder's construction and requires suitably formed cutting inserts.